JP3512177B2 - Packet receiving apparatus and packet transmitting method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet receiving device and a packet transmitting method used in packet transmission, and more particularly to a packet receiving device and a packet transmitting method for restoring a header transmitted by compression.

[0002]

2. Description of the Related Art Currently, as a typical protocol (communication procedure) used for transmitting packets on the Internet, RTP (Real-time Transport Protocol) is used.
ol), UDP (User Data Protocol), IP (Inte
rnet Protocol), and it is common to use these protocols in combination in packet transmission. In addition, these protocols are IETF (Internet Engin
eering Task Force).

In each of the above-mentioned protocols, a packet is generated by adding the following information as a header to the transmission data. That is, first, in RTP, a sequence number (hereinafter, “S
N ”) and a time stamp (hereinafter, abbreviated as“ TS ”as necessary) as time information are added to the data to generate an RTP packet.

Next, in UDP, the port number on the receiving side is added to the RTP packet to generate a UDP packet. Next, in IP, the Internet address (IP address) of the receiving side is added to the UDP packet to generate an IP packet. Then, this IP packet is transmitted to the receiving side.

Of these headers added by RTP, UDP, and IP, TS and SN are dynamic information that changes every time a packet is transmitted. The other information is static information (STATIC information) that remains unchanged after the communication is started.

Since such a header is added for each protocol, when communication is performed by a plurality of protocols, the header portion becomes long and packet transmission efficiency deteriorates. Therefore, there is a header compression technique as a technique for improving the transmission efficiency of packets by compressing and transmitting the header.

Regarding the compression method of each header added in RTP, UDP, and IP, the IETF makes it RF.
It is defined as C (Request For Comments) 2508. The header compression method specified in RFC2508 is
It is mainly defined for wired packet transmission such as the Internet.

On the other hand, ROHC (RObust Header Comp.) Is used as a header compression method currently proposed by IETF mainly for wireless packet transmission such as mobile telephone networks.
ression). This method, in the wireless section,
This is a header compression method that takes into consideration that the error occurrence rate during packet transmission tends to be higher than that in the wired section, and that it has high resistance to errors that occur during transmission.

In addition, since the frequency band that can be used is narrower in the wireless section than in the wired section, RF2 is used in ROHC.
As compared with the header compression method defined in 508, the header compression rate is further increased. ROHC is IET
At F, draft-ietf-rohc-rtp-09.txt is being standardized.

In this ROHC, there are two types of headers as shown in FIGS. 4A and 4B, which are called uncompressed (IR) packet and compressed (SO) packet, respectively.
In the header of the IR packet shown in FIG. 4A, parameters that are not changed during communication (IP address, port number, etc .: static information), parameters that change during communication (SN, TS, etc.), and the receiving side are headers. CRC (Cyclic Redundancy Ch
eck) bit is included.

The static information, TS, and SN are often transmitted at predetermined intervals. The compressed packet shown in FIG. 4B does not include the IP address, port number, TS, and ΔTS (TS increment), but includes a compression sequence number (hereinafter, abbreviated as SN ′ as necessary) and a CRC bit. . This SN 'is represented by only the lower few bits of the SN which is originally 16 bits.

In ROHC, the header is specifically compressed as follows. That is, the uncompressed header including the IP address and the port number is not transmitted for each transmission unit but is transmitted at a predetermined interval. If there is a certain regularity between the increment of SN and the increment of TS, only SN is transmitted, and the increment of TS is calculated from the increment of SN on the receiving side.

Further, with regard to SN, only the lower several bits are transmitted by the SO packet, and the bits of all SNs are transmitted only when a carry occurs. In this case, the transmitting side refers to reference information called a context to compress the header, and the receiving side refers to the same context as that used on the transmitting side to restore the header. In this case, the reference information indicates the information of the header transmitted last time.

Specifically, the lower bit of SN is selected and S
A method of creating N ′ will be described with reference to FIG. First, since packet 1 cannot send only the lower bits, the SN of 16 bits is transmitted as an IR packet as it is. Next, the transmitting side transmits packets 2 and 3 in this order, but the upper bits (1st to 12th bits) do not change between adjacent packets, so the lower 4 bits (13th to 16th bits) are transmitted. (Up to a bit) only. On the receiving side, by referring to the context, it is possible to restore the correct 16-bit SN with only the lower 4 bits.

For example, in the case of packet 2, only the lower 4 bits "0010" are transmitted. The receiving side determines that the remaining upper 12 bits are unchanged from packet 1, and sets SN to "000.
0 0000 0000 0010 "can be decompressed. Since the CRC is added to each compressed packet, it is possible to check whether the decompressed header is a correct header.

When the packet 17 is sent, a carry occurs and the lower 5th bit changes from 0 to 1.
Therefore, the lower 4 bits alone cannot be correctly transmitted. Therefore, in the packet 17, for example, the lower 6 bits "010000" of SN are transmitted. This allows the receiving side to restore the correct 16-bit SN.

Next, packet transmission / reception performed using ROHC will be described with reference to FIGS. 6 and 7. FIG. 6 is a block diagram showing the configuration of a conventional packet receiving device.
FIG. 7 is a sequence diagram for explaining a conventional packet transmission / reception procedure.

First, as shown in FIG. 7, the transmitting side (compressing side) transmits an IR packet containing static information, TS, SN, and CRC bits. After that, SO packets including the lower bit (SN ') of SN and the CRC bit are continuously transmitted. When the static information is not correctly transmitted, all the subsequent information cannot be correctly received, so that it is possible to prevent the loss of all information by transmitting IR packets periodically.

In the packet receiving device shown in FIG.
The reception signal received via the antenna 601 is received by the receiving unit 6.
In 02, a predetermined wireless reception process (for example, down conversion or A / D conversion) is performed, and a demodulation process is performed on the signal after the wireless reception process. The packet after the demodulation process is output to the header restoration unit 603, and the header restoration unit 603 restores the header. Restoring the header is done as described above.
The compressed sequence number SN ′ is restored by referring to the context which is stored in the buffer 606 and is the information of the previously transmitted packet. Specifically, on the restoration side (reception side), SN is restored from SN '(lower bit of SN), and R
The value of TS (time stamp) included in the TP header is S
Calculated from N, the RTP header, the UDP header, and the entire IP header are restored by the static information, SN, and TS.

The packet containing the restored header is CR
The data is output to the C unit 604, and the CRC unit 604 performs error detection by CRC. If no error is detected by CRC, it is output as a received packet. Also, at this time,
The content of the buffer 606 is updated to the context of the received packet, that is, the header according to the instruction of the context updating unit 605.

As described above, SN 'includes only the lower bits of SN, but the upper bits have already been received by the restoration side and can be predicted from the SN value of the restored packet. Can be restored. Even if the prediction is wrong, it is possible to prevent the erroneous SN from being restored because it is detected by the CRC check.

Next, the case where a bit error occurs in the header portion will be described with reference to FIG. As shown in FIG. 8, when a bit error occurs in the compressed packet 4 (SO), the decompression side decompresses the header as usual and then CRC is performed.
Upon detection, a bit error is detected in the compressed packet 4. In this case, it is determined that an error has occurred in the header part or the CRC bit, and the compressed packet 4 is discarded.

Next, the case where a bit error occurs in the IR packet will be described with reference to FIG. As shown in FIG. 9, when the IR packet 6 is received, the I
The bit error of the header of the R packet is detected. If a bit error is detected, packet 6 is discarded.

[0024]

However, as shown in FIG. 9, when a bit error occurs in an IR packet, discarding the packet as described above causes the following problems. That is, when a bit error is detected, it means that a bit error exists in any of the three places of static information, SN ′, and CRC bit or some of them. In this case, when a bit error occurs only in the static information (portion not related to header compression), the whole packet is discarded due to the result of CRC even if SN ′ is correctly received.

The present invention has been made in view of the above points, and provides a packet receiving apparatus and a packet transmitting method capable of correctly receiving a packet without discarding the packet even if an error occurs in a portion unrelated to header compression. The purpose is to provide.

[0026]

A packet receiving apparatus of the present invention is a packet receiving apparatus in which a header containing dynamic information and static information is compressed.
A packet receiving device for restoring a packet header,
Header decompression means for decompressing the compressed header, storage means for storing a header portion of a correctly received packet, and error detection for detecting an error in the decompressed header
Means and when an error is detected by the error detection means,
Header Nitsu after replacing the static information of the header part of the received static information of the restored header packet correctly
There are, when no error is detected by said error detection means, and outputs the packet as a received packet, comprising means for updating the header after replacing in said storage means, and said error detection means , Restored head
The header part of the packet in which the static information of the packet was correctly received.
An error was detected in the header after replacing it with the static information of
If it is, a configuration that discards the packet.

The packet receiving apparatus of the present invention has the above-mentioned configuration in which a part of the restored header is static information that remains unchanged after communication is started. Further, the packet transmitting apparatus of the present invention is characterized by performing wireless communication with the packet receiving apparatus.

According to these configurations, even if a transmission error occurs in the static information in the header of the packet (IR packet) including the uncompressed header, the static information already correctly received by the receiving side is used instead. Since it can be used, the probability that the receiving side discards the IR packet can be reduced.

The packet transmission method of the present invention uses dynamic information and
The header of the packet that contains the compressed static information is
A packet transmission method for restoration, in which the transmitting side
Periodically transmitting a packet containing an uncompressed header and transmitting a packet containing a compressed header, a header decompressing step of decompressing the compressed header at the receiving side, the uncompressed header and the
An error detecting step of detecting an error in the restored header, a storing step of storing a header portion of a packet correctly received, and a static information of the restored header when an error is detected in the error detecting step. Of the header after replacing the with the static information in the header part of the correctly received packet.
When the error is not detected in the error detecting step, the packet is output as a received packet, and the header after replacement is updated.
However, in the error detection step, the static information of the restored header is
Information in the header part of the packet for which the information was received correctly
If an error is detected in the header after replacing
If so, the packet is discarded .

According to this method, even if a transmission error occurs in the static information in the header of the packet (IR packet) including the uncompressed header, the static information already correctly received by the receiving side is used instead. Therefore, the probability that the receiving side discards the IR packet can be reduced.

Furthermore, according to this method, the IR
Since the packet can be transmitted, even if the reception side fails to receive the IR packet, the next IR packet can be correctly received if it is received.

The recording medium of the present invention includes dynamic information and static information.
Decompressing the header of a packet having a compressed header containing a packet reception program, which is a computer-readable storage medium, and a decompression procedure for decompressing the compressed header; Headers and
And an error detection procedure for detecting an error in the restored header
When a storage procedure for storing the correct header portion of the received packet, when an error is detected by said error detection procedure, the header portion of the received static information of the restored header packet correctly Static Header after replacing with information
Regarding the above, when no error is detected in the error detection procedure, the packet is output as a received packet, and the header after replacement is updated.
In the error detection procedure, the static information of the restored header is
Information in the header part of the packet for which the information was received correctly
If an error is detected in the header after replacing
If so, the packet is discarded .

The packet receiving program of the present invention is a dynamic
A packet with a compressed header containing information and static information.
The packet receiving program for restoring the header, and restoring the compressed header, the said compressed
Detect missing headers and errors in the restored headers
A step, and storing the correct header portion of the received packet, when an error is detected in the step of detecting the error, the header portion of the received static information of the restored header packet correctly For the header after being replaced with static information , the error detection step
When no error is detected in-up, and outputs the packet as a received packet, possess updating the header after replacing, and to detect the error
The step that correctly receives the static information of the restored header.
Replaced with static information in the header of the received packet
If an error is detected in the subsequent header, the packet
It can be operated by a computer.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Since CRC bits are included in the headers of uncompressed packets and compressed packets, when bit errors occur in these headers, an error is detected and the packet is discarded. can do. However, in the case of a non-compressed packet, even if a bit error occurs in static information (portion that does not change during communication) such as the source IP address, the packet is discarded when the CRC detects an error.

This is a part related to compression (eg SN).
C without distinguishing between the part that is not related to compression (static information)
This is because the packet was discarded based only on the RC result.
The present inventors have paid attention to this point, and use the fact that the static part is stored in the buffer as the context, and the static part is used to restore the received packet using what has already been correctly received. The present invention has been found out that it is possible to determine whether or not a portion related to compression is correctly received by performing CRC again.

That is, the essence of the present invention relates to the compression by re-checking the error using the already received static information when the transmission bit error occurs in the static information and the header cannot be received correctly. It is to judge whether or not the part has been correctly received (if no bit error is recognized, it is judged that the bit error has occurred only in the static information), and to correctly receive the received packet in which the bit error has occurred.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, when a bit error is detected by the CRC in the packet received by the packet reception device, the static information that has already been correctly received is read from the buffer, and the CRC is performed again.
A case will be described in which it is determined whether or not a portion related to compression has been correctly received.

FIG. 1 is a block diagram showing the configuration of a packet receiving apparatus according to an embodiment of the present invention. Note that, here, a case where a packet is transmitted via a wireless line will be described.

In the packet receiving device shown in FIG.
The receiving unit 102 performs a predetermined wireless reception process (for example, down-conversion or A / D conversion) on the packet received via the antenna 101, and then performs a demodulation process on the signal after the wireless reception process. . The received packet after demodulation processing is output to the header restoration unit 103.

The header restoration unit 103 restores the header of the received packet by referring to the context stored in the buffer 106, and the CRC unit 1 restores the packet after the header restoration.
Output to 04. The CRC unit 104 includes the header restoration unit 10
CRC is applied to the header of the packet output from
The packet after RC is output as a received packet. Also, the CRC unit 104 instructs the context updating unit 105 to update the context when there is no bit error in the CRC. The context updating unit 105 uses C
The context stored in the buffer 106 is updated according to the instruction from the RC unit 104.

The header re-restoring unit 107 has a CRC unit 104.
When an error is detected from the command, the static information stored in the buffer 106 is replaced with the static information of the received packet to restore the packet again, and the restored packet is CR.
It is output to the C unit 104.

FIG. 2 is a block diagram showing a configuration of a packet transmission device for performing wireless communication with the packet reception device according to the embodiment of the present invention. This packet transmission device periodically transmits static information.

In the packet transmitting apparatus shown in FIG. 2, the dynamic information generator 201 generates dynamic information such as TS and SN regarding data. The static information generation unit 202
Generate static information such as P address and port number.
The CRC bit addition unit 20 converts these dynamic information and static information.
Output to 3.

The CRC bit addition section 203 adds a CRC bit to the header information that is a collection of static information and dynamic information, and outputs a signal with the CRC bit added to the transmission packet selection section 205.

The transmission packet selection unit 205 selects an IR packet when the counter 204 for counting the number of times the packet has been transmitted exceeds a predetermined number, generates a transmission packet, and resets the counter 204. Further, the transmission packet selection unit 205 selects the SO packet and generates the transmission packet if the counter 204 is less than the predetermined number. When selecting an SO packet, the first embodiment
Perform the header compression described in.

The transmission packet is output to the transmission section 206, and undergoes modulation processing and predetermined wireless transmission processing (for example, D / A).
Conversion, up-conversion, etc.) and then transmitted via antenna 207.

With this configuration, an IR packet containing static information can be transmitted periodically, so that even if the reception side fails to receive the IR packet, the next IR packet can be received. Packets can be correctly received.

Next, a packet transmission method using the packet receiving device having the above configuration will be described with reference to FIGS. Here, the case where the SN is 16 bits will be described, but the SN may be other than 16 bits.

First, on the transmitting side, the static information generation unit 202
The IR packet including the static information generated in step S1, the TS and SN generated in the dynamic information generating unit 201, and the CRC bit is transmitted, and then the SO packet including the compressed SN ′ and the CRC bit is transmitted. This IR packet and S
The O packet is selected by the transmission packet selection unit 205. The IR packet is periodically transmitted when the count of the counter 204 exceeds a predetermined number.

In transmitting IR packets, it is desirable to reduce the frequency of transmitting IR packets with time. This is because at the initial stage of communication, it is considered that few devices are receiving IR packets correctly, so at this stage, the frequency of IR packet transmission should be set relatively high and the IR packets should be transmitted correctly over time. When the number of receiving devices increases, the frequency of transmitting IR packets is reduced. As a result, the frequency of transmitting IR packets decreases with time, and the transmission efficiency can be increased. Note that this control can be performed by increasing the predetermined number of the counter 204 with time.

When transmitting an IR packet, as for SN, as shown in FIG. 5, in packet 1, since only the lower bits cannot be transmitted, SN "000 of 16 bits is transmitted.
0 0000 0000 0001 "is transmitted as an IR packet as it is. Next, the transmitting side sequentially transmits packet 2 and packet 3, but the upper bits (from the 1st bit to the 12th bit: context part) are close to each other. Since it does not change between packets, only the lower 4 bits (“0010” for packet 2 and “0011” for packet 3) are transmitted.

The packet 1 is received by the packet receiving apparatus shown in FIG.
If no bit error is detected as a result of RC, it is output as a received packet and also output to the context updating unit 105. The CRC result of the CRC unit 104 is output to the context updating unit 105.

The context updating unit 105 includes the CRC unit 1
When receiving the result from 04 that there is no bit error, CRC
The header of the received packet output from the unit 104 is stored in the buffer 106. As a result, the SN portion is updated along with the latest static information.

After the packet 2 is received by the packet receiving apparatus shown in FIG. 1, the header is restored by the header restoring unit 103. That is, in packet 2, only the lower 4 bits "0010" are transmitted as SN '. Therefore, the header restoration unit 103 restores SN ′ by referring to the context portion stored in the buffer 106. Specifically, the context part "0000 0000 0000" and 16-bit SN "0000 00" from the SN '"0010" of the transmitted packet.
00 0000 0001 "is restored, and the value of TS (time stamp) included in the RTP header is calculated from SN,
The RTP header, the UDP header, and the entire IP header are restored by the static information, SN, and TS.

Packet 2 whose header has been restored in this way
Is sent to the CRC section 104, and the CRC section 104
Is done. If the CRC detects an error, packet 2
Is output to the header re-restoring unit 107, and the fact that the CRC is NG is output to the header re-restoring unit 107 (FIG. 3A).

In this case, it is not known whether the CRC error is a portion related to compression (a portion other than static information) or a portion not related to compression (a portion of static information). For this reason, the portion not related to compression (static information portion) is replaced with the correctly received portion not related to compression (static information portion), and CRC is performed again. This will make the CRC
If an error is detected again by, it is found that the CRC error is in a portion related to compression (a portion other than static information).

Therefore, if an error is detected even if the correct static information is replaced, the part of the CRC error related to compression (SN ') is incorrect and the packet cannot be used. Therefore, the packet is discarded. To do. If the correct static information is replaced and no error is detected, it is considered that the static information is incorrect and the packet can be used by replacing the static information. Therefore, the packet is output as a received packet. To do. As a result, in the conventional method, the packet that has been discarded can be used, and the packet transmission efficiency can be improved.

Specifically, the header re-restoring unit 107 extracts the latest correct static information stored in the buffer 106, and uses that static information as the static information of the packet shown in FIG. replace. The header packet is output to the CRC unit 104 in this replaced state. Similarly, the CRC unit 104 performs CRC again on the packet with the static information replaced.

If no error is detected by the CRC, it is considered that the static information is incorrect and the packet can be used by replacing the static information. Therefore, the packet is output as a received packet ( Figure 3
(B)). Then, the packet is output to the context updating unit 105. Further, the result of the CRC repeated by the CRC unit 104 is output to the context updating unit 105.

The context updating unit 105 includes the CRC unit 1
When receiving the result from 04 that there is no bit error, CRC
The header portion of the received packet output from the unit 104 is stored in the buffer 106. As a result, the SN portion is updated along with the latest static information.

On the other hand, if an error is detected by CRC,
Since it is considered that the packet related to compression such as SN 'is incorrect and the packet cannot be used even if the static information is replaced, the packet is discarded (FIG. 3).
(C)).

As described above, in the present embodiment, the portion not related to compression (static information portion) is replaced with the correctly received portion not related to compression (static information portion), and CRC is performed again. And clarify which part has the error. Then, if an error is detected even if the correct static information is replaced, the packet is discarded, and if the correct static information is replaced and no error is detected, the packet is output as a received packet. This allows
In the conventional method, the discarded packet can be used, and the packet transmission efficiency can be improved.

In this embodiment, when a carry occurs in the packet 16 as shown in FIG. 5, by changing the bit number of the context part, that is, by setting the context part to "010000", Packet transmission can be performed as described above.

The present invention is not limited to the above-mentioned embodiments, but can be implemented with various modifications. For example, in the above embodiment, the case where the packet transmission is performed by the packet receiving device and the packet transmitting device has been described, but the present invention is not limited to this, and the packet transmission can be performed by software.

For example, a program for performing the above packet transmission is stored in advance in a ROM (Read Only Memory),
The program may be operated by a CPU (Central Processor Unit).

Further, the program for performing the above packet transmission is stored in a computer-readable storage medium, and the program stored in the storage medium is stored in the RAM of the computer.
You may make it operate | move according to the program by recording in (Random Access memory). Even in such a case, the same operation and effect as those of the above-described embodiment are exhibited.

In the above embodiment, the header restoration is performed by the header restoration unit 103 and the header restoration is performed by the header restoration unit 107. However, in the present invention, the header restoration and the header restoration are performed. The restoration may be performed by the same circuit.

The packet receiving device of the present invention and the packet transmitting device for wirelessly communicating with the packet receiving device are a communication terminal device used in a digital wireless communication system,
For example, it can be applied to a communication terminal device that performs voice communication and image communication, a communication relay device that performs voice communication and image communication, and the like.

[0069]

As described above, according to the present invention, a portion not related to compression (static information portion) is replaced with a correctly received portion not related to compression (static information portion), and CRC is performed again. To clarify which part has the error. Then, if an error is detected even if the correct static information is replaced, the packet is discarded, and if the correct static information is replaced and no error is detected, the packet is output as a received packet. This allows
Even if an error occurs in a received packet via a transmission line having a bit error, the probability of discarding data can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a packet reception device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a packet transmission device that performs wireless communication with the packet reception device according to the embodiment of the present invention.

FIG. 3 is a diagram for explaining an operation in the packet reception device according to the embodiment of the present invention.

FIG. 4 is a schematic diagram showing a packet configuration.

FIG. 5 is a diagram showing an example of compression of sequence numbers.

FIG. 6 is a block diagram showing a configuration of a conventional packet receiving device.

FIG. 7 is a sequence diagram for explaining a conventional packet transmission / reception procedure.

FIG. 8 is a sequence diagram for explaining a case where an error occurs in a compressed packet in the conventional packet transmission / reception procedure.

FIG. 9 is a sequence diagram for explaining a case where an error occurs in an uncompressed packet in the conventional packet transmission / reception procedure.

[Explanation of symbols]

101,207 antenna 102 receiver 103 header restoration unit 104 CRC section 105 Context update part 106 buffer 107 header restoration section 201 Dynamic information generator 202 Static information generator 203 CRC bit addition unit 204 counter 205 Transmission packet selection unit 206 transmitter

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koichi Hata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Kirsten Blumeister Kurzerweg 3, D64295 Darmstadt Germany (56) Reference Documents JP-A-1-177731 (JP, A) JP-A-8-331103 (JP, A) International publication 00/079763 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 1/00

Claims (6)

(57) [Claims] 1. A header including dynamic information and static information is compressed.
In the packet receiver that restores the header of the packet
And a header decompression unit for decompressing the compressed header, a storage unit for storing a header portion of a correctly received packet, and an error in the decompressed header.
An error detection unit, wherein when an error is detected by the error detection means, after replacing the static information of the header part of the received static information of the restored header packet correctly f
For header, when an error is not detected by said error detection means, and outputs the packet as a received packet, comprising means for updating the header after replacing in said storage means, wherein the error detection Means is restored
The static information in the header of the
Error in header after replacing with static information of da part
When the packet is detected , the packet receiving device discards the packet. 2. The packet receiving apparatus according to claim 1, wherein a part of the restored header is static information that remains unchanged after communication is started. 3. A packet transmitting device, which performs wireless communication with the packet receiving device according to claim 1 or 2. 4. A header containing dynamic information and static information is compressed.
In the packet transmission method to recover the header of the packet
Then, the transmitting side periodically transmits the packet including the uncompressed header, and the step of transmitting the packet including the compressed header, and the receiving side, the header decompressing step of decompressing the compressed header. , The pressure
Check for errors in uncompressed header and the restored header.
An error detection step of leaving, the correctly received packets and storing step of storing the header portion, when an error is detected in the error detection process, the received static information of the restored header packet correctly With respect to the header after replacement with the static information of the header part, when no error is detected in the error detection step, the packet is output as a received packet, and the header after replacement is updated. And the error detection step restores
The static information in the received header to the correctly received packet.
Incorrect about header after replacing with static information of header
If the packet is detected, the packet is discarded and the packet is transmitted. 5. A header containing dynamic information and static information is compressed
A computer-readable storage medium that stores a packet reception program that restores the header of a compressed packet, and a header restoration procedure that restores the compressed header, the uncompressed header, and the restored header.
Error detection procedure to detect an error in the header, a storage procedure to store the header part of a correctly received packet, and a static information of the restored header correctly when an error is detected in the error detection procedure. Regarding the header after replacing it with the static information of the header part of the received packet, when no error is detected in the error detection procedure, the packet is output as a received packet and the header after replacement is updated. and procedures for, only contains the, the error detection procedure
Received the static information in the restored header correctly
After replacing with the static information in the packet header,
If an error is detected for a packet, the packet is dropped
A recording medium characterized by: 6. A header containing dynamic information and static information is compressed
Packet reception program that restores the header of the
RAM, the step of decompressing the compressed header.
The uncompressed header and the decompressed header.
Test detecting errors Da, and storing the correct header portion of the received packet, the error
When an error is detected in the sending step , the header after replacing the static information of the restored header with the static information of the header portion of the correctly received packet,
Yes when no error is detected in the step of detecting an error, outputs the packet as a received packet, and updating the header after replacing the
And the step of detecting said error is
Correctly received the static information of the header part of the packet
An error was detected in the header after replacing it with static information.
If received, the packet receiving program is characterized in that the packet is discarded .